PRIMARY STRUCTURE OF 2S ALBUMIN FROM SEEDS OF LUPINUS-ALBUS

The 2S albumin from the seeds of white lupin (Lupinus albus L.) was pu rified by ammonium sulfate precipitation and ultrafiltration followed by anion-exchange and reversed-phase HPLC. The complete amino acid seq uences of the large and the dominating small subunit were determined b y automated Edman degradation of the reduced and S-pyridylethylated po lypeptides and of their enzymatic fragments. The small subunit of the 2S albumin (a) consists of 37 amino acid residues resulting in a molec ular mass M(r) of 4407. The large subunit (b) contains 75 amino acid r esidues (M(r) = 8827). The two polypeptide chains are linked by two in terchain disulfide bonds (Cys(a8)-Cys(b24) and Cys(a20)-Cys(b13) or, m ore probably, Cys(a20)-Cys(b12)). In addition, the large polypeptide c ontains two intrachain disulfide bridges (Cys(b26)-Cys(b68) and Cys(b1 2)-Cys(b60) or, more probably, Cys(b13)-Cys(b60)) and one free sulfhyd ryl group (Cys(b40)). A high degree of homology (88%) exists between t he primary structure of the 2S albumin from L. albus and that of a com parable 2S protein from L. angustifolius, designated conglutin delta.